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Wastegate actuators


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Hi all just after a bit of advice.


I tested my actuators with a pump and dial gauge as per the manual. The actuator rod is supposed to move 0.4 mm with 0.35 bar pressure. 
Mine move 0.4 mm at 0.4 bar and 0.5 bar.

The car runs fine and the boost pressure seems ok. I’m curious as to what this test means? I assume that 0.35 bar is the pressure at which the valve opens. Manually controlling the boost pressure. I think the boost is electronically controlled (increased)by the solenoid valve? So does it matter that mine open at a slightly higher pressure?

I’m sure if I try and adjust the rusted nuts on the valve they will break. 
 

Cheers Andy
 

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  • Gold FFM

Hi Andy,

It is not clear to me how smart the ECU is in respect to controlling boost in this way. 

The ECU controls the wastegates by managing the boost pressure they see by use of the boost solenoid valve as you correctly noted. The ECU bleeds pressure from the valve until the required boost is seen at the MAP sensor (I am guessing), at this point (or maybe a fraction before) it will allow some boost past the solenoid valve to the wastegates allowing them to open and limit how much boost the turbos make. 

Naturally you don't want all boost to arrive at the wastegate capsules since they would open at .35 bar preventing intake pressures much beyond this, so the solenoid valve bleeds some pressure off and allows only enough through when the ECU tells it to.

The bit that is unclear to me is how the ECU manages situations like yours, will it just open the solenoid valve a little more when intake boost pressures rise above the expected level, thus controlling boost successfully, or does it just stick rigidly to a built in map that believes it has done it's job and the wastegate should be opening correctly, this would lead to slightly elevated boost conditions I think.

Now I would have expected the ECU to be smart and open the solenoid valve a little more if boost was rising above the desired amount but if that was the case I can't see why increasing the spring rate of the wastegate capsules (so that they need more pressure than standard to open) increases boost, (but I'm pretty sure it does) since the ECU would just allow more pressure past the solenoid valve and keep it all in check.

Hopefully someone with a deeper understanding can explain properly what does happen assuming my comments are clear, it do wonder if I've just written a load of gibberish but can't be bothered to re-read it to check. 🤦‍♂️

cheers

-Chris

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It is just a calibration point for the base mechanical boost.  Meaning that if you loose electronic boost control, the boost will be mechanically limited to around 5psi.  In Andy's case, his mechanical base setting is slightly high, meaning that is he looses electronic control, then he will have a slightly higher base boost developing (closer to 7psi).

The ECU controls the target boost based on the wastegate duty cycle (expressed as a %). It is basically a square wave with the duration relating directly to the % of time that the solenoid is bleeding air, meaning 50% WGDC = solenoid actuation half of the time.

 The boost curves that are configured within the ECU calibration are based are values for the WGDC in gear, over the rev range.  In a stock set-up, the calibration point just ensures consistency with those values. 

A minor variation is not going to have a significant change in real-world boost.

Of course if you significantly strengthen the wastegate actuator springs, you will change the pre-load and the behaviour for a given WGDC.  

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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  • ramjet changed the title to Wastegate actuators
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Fight you for 'em 😈

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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So I got the secondhand forge wastewater actuators. One was in working order the other had a broken spring. I’ve stripped and cleaned them and ordered some new springs. 

The weakest spring is the green one which is 0.7 bar. I assume this means that my base setting is now 0.7 instead of 0.35 bar. 
If  this is the case I wonder how the ecu will control boost if at all?

When I’ve assembled them I can test them to see what the actual pressure is to start opening. 
 

Also a fair bit of corrosion on the backside where they bolt to the turbo housing. I guess it’s because of the dissimilar metals reacting. 
 

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  • Gold FFM

You'll be fine, you can still calibrate them in accordance with the manual, it's a matter of pre-load on the spring and how much. The springs are labelled 0.7bar but it doesn't really mean anything, they have a strength of X and with the right pre-load adjustment it works fine. 🙂 

cheers

-Chris

 

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Chris is right.  The green spring is very similar to the stock spring and can be calibrated to the correct base setting.

Next in strength is the yellow spring, which you will not be able to calibrate down to the factory base setting.

 

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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